Crate ed25519_dalek

ed25519 signatures and verification

Example

Creating an ed25519 signature on a message is simple.

First, we need to generate a Keypair, which includes both public and secret halves of an asymmetric key. To do so, we need a cryptographically secure pseudorandom number generator (CSPRING), and a hash function which has 512 bits of output. For this example, we'll use the operating system's builtin PRNG and SHA-512 to generate a keypair:

extern crate rand;
extern crate sha2;
extern crate ed25519_dalek;

use rand::Rng;
use rand::OsRng;
use sha2::Sha512;
use ed25519_dalek::Keypair;
use ed25519_dalek::Signature;

let mut cspring: OsRng = OsRng::new().unwrap();
let keypair: Keypair = Keypair::generate::<Sha512>(&mut cspring);

We can now use this keypair to sign a message:

let message: &[u8] = "This is a test of the tsunami alert system.".as_bytes();
let signature: Signature = keypair.sign::<Sha512>(message);

As well as to verify that this is, indeed, a valid signature on that message:

let verified: bool = keypair.verify::<Sha512>(message, &signature);

assert!(verified);

Anyone else, given the public half of the keypair can also easily verify this signature:

use ed25519_dalek::PublicKey;

let public_key: PublicKey = keypair.public;
let verified: bool = public_key.verify::<Sha512>(message, &signature);

assert!(verified);

Serialisation

PublicKeys, SecretKeys, Keypairs, and Signatures can be serialised into byte-arrays by calling .to_bytes(). It's perfectly acceptible and safe to transfer and/or store those bytes. (Of course, never transfer your secret key to anyone else, since they will only need the public key to verify your signatures!)

use ed25519_dalek::{PUBLIC_KEY_LENGTH, SECRET_KEY_LENGTH, KEYPAIR_LENGTH, SIGNATURE_LENGTH};

let public_key_bytes: [u8; PUBLIC_KEY_LENGTH] = public_key.to_bytes();
let secret_key_bytes: [u8; SECRET_KEY_LENGTH] = keypair.secret.to_bytes();
let keypair_bytes:    [u8; KEYPAIR_LENGTH]    = keypair.to_bytes();
let signature_bytes:  [u8; SIGNATURE_LENGTH]  = signature.to_bytes();

And similarly, decoded from bytes with ::from_bytes():

let public_key: PublicKey = PublicKey::from_bytes(&public_key_bytes)?;
let secret_key: SecretKey = SecretKey::from_bytes(&secret_key_bytes)?;
let keypair:    Keypair   = Keypair::from_bytes(&keypair_bytes)?;
let signature:  Signature = Signature::from_bytes(&signature_bytes)?;

Using Serde

If you prefer the bytes to be wrapped in another serialisation format, all types additionally come with built-in serde support by building ed25519-dalek via:

$ cargo build --features="serde"

They can be then serialised into any of the wire formats which serde supports. For example, using bincode:

extern crate serde;
extern crate bincode;

use bincode::{serialize, Infinite};

let encoded_public_key: Vec<u8> = serialize(&public_key, Infinite).unwrap();
let encoded_signature: Vec<u8> = serialize(&signature, Infinite).unwrap();

After sending the encoded_public_key and encoded_signature, the recipient may deserialise them and verify:

use bincode::{deserialize};

let message: &[u8] = "This is a test of the tsunami alert system.".as_bytes();
let decoded_public_key: PublicKey = deserialize(&encoded_public_key).unwrap();
let decoded_signature: Signature = deserialize(&encoded_signature).unwrap();

let verified: bool = decoded_public_key.verify::<Sha512>(&message, &decoded_signature);

assert!(verified);

Structs

ExpandedSecretKey	An "expanded" secret key.
Keypair	An ed25519 keypair.
PublicKey	An ed25519 public key.
SecretKey	An EdDSA secret key.
Signature	An EdDSA signature.

Constants

KEYPAIR_LENGTH	The length of an ed25519 EdDSA Keypair, in bytes.
PUBLIC_KEY_LENGTH	The length of an ed25519 EdDSA PublicKey, in bytes.
SECRET_KEY_LENGTH	The length of an ed25519 EdDSA SecretKey, in bytes.
SIGNATURE_LENGTH	The length of an ed25519 EdDSA Signature, in bytes.